There was a mantra inside the defensive line meeting rooms and on the Broncos’ practice field this month, and it came straight from the mouth of defensive line coach Wayne Nunnely.

“Knock ’em back. Nobody runs on the Broncos,” Nunnely said. “One of the things that I’ve prided myself on in the years that I’ve been in the league is having a good run defense. If you have a good run defense, you got a chance to win.”

So it must have eaten up Nunnely’s insides during the final weeks of the 2009 season, as the Broncos’ defense allowed hundreds of rushing yards, often in large chunks, to players such as Pittsburgh’s Rashard Mendenhall (155 yards Nov. 9), Oakland’s Michael Bush (133 yards Dec. 20) and Kansas City’s Jamaal Charles (a whopping 259 yards Jan. 3).

The memories (and game tape) of performances like that fueled the Broncos’ offseason strategy, when the team signed three bigger veteran defensive linemen (ends Justin Bannan and Jarvis Green and nose tackle Jamal Williams), and cut a defensive end (Kenny Peterson) and inside linebacker (Andra Davis), each of whom started at least 13 games.

The goal was simple: Build a big, unmovable wall up front.

“That was the priority,” Nunnely said.

The Broncos have had two games to debut their revamped run defense, and the results, well, haven’t shown as dramatic a transformation as many had hoped.

The Broncos have allowed 342 rushing yards in preseason games against Cincinnati and Detroit, an average of 171 per game. That ranks the Broncos last in the NFL in the preseason. The 31st -ranked team, the Jacksonville Jaguars, has allowed only 294.

“It’s fair to judge. I think whoever is out there has to do what we’re trying do,” coach Josh McDaniels said. “I think we’ve played good run defense in camp. There’s also been some things we’ve needed to fix. From the Detroit game the other day, we didn’t do a particularly good job of containing the edge, and then inside we created a few seams in there that we shouldn’t have created, but I think we have the right idea.”

Denver’s starters allowed 24 rushing yards in the first quarter of the first game at Cincinnati and 68 yards in the first half last week against Detroit. Lions’ rookie running back Jahvid Best rushed eight times for 49 yards — an average of 6.1 yards per carry — in the first half last week and was particularly effective with cut-back runs when he darted to the outside of the formation. Best broke for 11- and 15-yard carries in the first quarter.

“Run defense is all about having the right attitude and the right mentality, and looking at the first two games, we did all right, there were some positives, but there’s a lot to work on,” Bannan said.

The starting defense will look different Sunday night against Pittsburgh, with a retooled look in the linebacker corps. Inside linebacker D.J. Williams is scheduled to make his preseason debut after missing two games with an undisclosed injury, and Mario Haggan has moved back inside after starting the past two games at outside linebacker. Both are moves the team is hoping will substantially improve the run defense.

Robert Ayers and Jarvis Moss are expected to be the starting outside linebackers.

“I think when they’re all in there and they’re all healthy and they’re all trying to play together, I think we can be a good run defense,” McDaniels said. “I think that, I really do.”

The Broncos’ run defense ranks last in the NFL through the first two preseason games, with an average of 171 yards allowed. The Broncos have made some changes at inside linebacker for the third preseason game Sunday night against Pittsburgh.

In: Mario Haggan

Out: Akin Ayodele

Goal: Ayodele started the first two preseason games, but was cut Tuesday when the team decided to move Haggan back inside where he will be better able to use his size and strength.

In: D.J. Williams

Out: Joe Mays/Wesley Woodyard

Goal: Williams is one of the team’s most experienced players and sure tacklers. He’s a three-down player strong against the run and pass.

Avalanche defenseman Erik Johnson had butterflies before Sunday's game against the Detroit Red Wings. It wasn't because of the big-name opponent, but rather his return from a 13-game injury absence and being stoked to rejoin a team in a playoff push and looking for its third postseason appearance in 10 years.